2.4.2. Superoxide Dismutase Mimetic Activity (SOD)

SOD activities for nanoparticles and nanoparticle conjugates of each synthesis method were measured using a home-built assay, reliant on a xanthine/hypoxanthine redox couple and WST-1 dye. In addition, the reduction of WST-1 was utilized to assess the kinetics of the reaction. The protocol was slightly adjusted from Peskin [18] study. Briefly, superoxide was generated by a 0.1 mM hypoxanthine/xanthine oxidase system. The generation rate of superoxide was controlled by adjusting the xanthine oxidase concentration, resulting in an absorbance change at 438 nm of approximately 0.025 units per minute. Each assay was conducted at room temperature for 10 min in a 96-well plate with a total volume of 240 μL containing 20 μL of the sample. Tris buffer 50 mM of pH 7.5 was used for all reactions. The SOD activity is calculated based on below equation: